Magnetoelasticity is defined as the sensitivity of a ferromagnetic material's magnetic characteristics to mechanical stress. Stress exerted on the ferromagnetic material produces a corresponding mechanical strain within the material. A ferromagnetic material having nonzero magnetoelastic coefficient is herein referred to as a magnetoelastic material. When a magnetoelastic material is subjected to alternating mechanical pressures, an alternation of its magnetic properties is correspondingly produced. When a magnetoelastic material subject to mechanical stress carries nonzero magnetic flux, the magnetic flux correspondingly changes with pressure applied to the ferromagnetic material. A changing magnetic flux is able to induce electrical signals and power by the mechanism of electromagnetic induction.
Magnetostriction is defined as a ferromagnetic material's ability to produce mechanical stress and strain causing changes in shape or volume, in a manner that corresponds to the magnetic polarization of the ferromagnetic material. A ferromagnetic material having non-zero magnetostriction is herein referred to as a magnetostrictive material. When a magnetostrictive material carries alternating magnetic flux, its internal stresses and physical dimensions vary corresponding to the magnetic field. All ferromagnetic materials have some degree of magnetostriction, and some degree of magnetoelasticity.
Vibration or alternating pressure within a medium is acoustic energy. Magnetoelastic materials are able to convert acoustic energy into magnetic energy. Conversely, magnetostrictive materials are able to convert magnetic energy into acoustic energy. Electromagnetic induction is able to exchange electrical energy with magnetic energy. The combination of electromagnetic induction, and magnetostriction and/or magnetoelasticity, provides a bridge between electrical and acoustic energy.
Ferromagnetic materials are often both magnetoelastic and magnetostrictive. However, some magnetic materials exhibit magnetostriction and magnetoelasticity which are not equal in magnitude.
Ferro-magnetic materials consist of magnetic dipoles which can be polarized magnetically. A complimentary class of ferro-electric materials consists of electric dipoles which can be polarized electrically. Piezoelectric materials contain ferroelectric dipoles capable of permanent polarization. Piezoelectric materials are generally well known as materials able to convert electrical energy to acoustic energy.